The present invention relates generally to lawn mower starting mechanisms and more particularly concerns a mechanical interlock mechanism which under certain conditions, prevents starting of an engine powered mower of the type in which the starter pinion advances into engagement with the flywheel during the starting process.
Due to certain safety considerations, it is sometimes desirable to prevent engagement between the starter pinion and flywheel to protect against starting of the engine of a gas powered lawn mower when the lawn mower is in a predetermined condition. One condition in which this may be highly desirable, applies to self-propelled gas powered mowers, that is, mowers in which the engine also provides forward drive for the mower. With such mowers, it is advantageous to have a mechanism preventing starting of the engine with the wheel drive mechanism engaged. Starting of the mower with the drive engaged could possibly result in operator loss of control, with the attendant hazards such loss of control involves.
It is known to provide an electronic module on mowers which senses engagement and disengagement of the wheel drive mechanism, and electrically prevents starting by grounding the magneto on said mowers during engagement when the motor is not operating. It is, however, necessary to provide such modules with a built-in memory feature, so that they do not ground the magneto each time engagement occurs, but only when starting is attempted with the drive engaged. Such modules and their sensors are unusually expensive and complicated in design, and due to their complicated design, of questionable reliability.
One example of a mechanical starter interlock is found in U.S. Pat. No. 3,739,763 issued to R. J. Berry et al. The Berry et al patent discloses an interlock mechanism for use with Bendix type recoil starters in which a starter pinion advances up a helical worm gear to engage the engine flywheel. The mechanism disclosed in Berry et al is an engine clutch actuated linkage which forces a leg of a starter spring carried on the starter pinion to engage a slot in a bracket, thereby impeding advance of the starter pinion into engagement with the flywheel during clutch engagement.
The starting interlock apparatus of the present invention was developed to provide a positive acting, highly reliable yet inexpensive lock-out device. It should be understood that the lock-out apparatus of the present invention is not limited to applications preventing engine starting during engagement of a mower drive mechanism. On the contrary, the invention could, of course, be used to prevent engine starting in response to other predetermined conditions of the mower.